Watch 402 Index listings

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds value beyond these by explicitly stating "does not send payment headers or paid calls," which clarifies financial side effects not covered by the hints alone. It also describes the kind of insights the lookup provides (spot down services, etc.), but does not elaborate on pagination or response format, keeping it just below a perfect score.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences, each with a distinct purpose: what the tool does, when to use it, and a safety clarification. It is fully front-loaded with the action verb and resource. No redundant or filler words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, but the description explains the practical utility (spot down services, invalid payment requirements, unverified domains). It covers the tool's purpose, use cases, and safety. Missing details like pagination or return counts are not explicitly stated, but the simplicity of the tool and the rich schema/annotations make this adequate with only minor gaps.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description mentions provider, domain, endpoint URL, and search term, but this effectively mirrors the q parameter's schema description ('402 Index search term, provider name, domain, service URL, or endpoint URL'). No additional parameter semantics are added beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: "Look up public 402 Index service records by provider, domain, endpoint URL, or search term." This clearly distinguishes the tool from siblings by explicitly stating it handles public metadata and does not send payment headers or paid calls, contrasting with x402_paid_paths.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides explicit usage context: "Use this before listing, outreach, launch review, or re-check work" and explains what it can reveal (down services, invalid payment requirements, unverified domains). It also includes an exclusion: "This is public metadata only and does not send payment headers or paid calls," guiding when not to use it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.